The technical field of this invention is phototherapy and, in particular, instruments employing optical fibers or other flexible light waveguides to deliver radiation to a targeted biological site.
Fiber optic phototherapy is an increasingly popular modality for the diagnosis and/or treatment of a wide variety of diseases. For example, some have proposed the use of fiber-delivered radiation to treat artherosclerotic disease. U.S. Pat. No. 4,878,492 (Sinofsky et al. '492), herein incorporated by reference, discloses the used of infrared radiation to heat blood vessel walls during balloon angioplasty in order to fuse the endothelial lining of the blood vessel and seal the surface. Another application of fiber-delivered radiation is disclosed in U.S. Pat. No. 5,053,033 (Clarke '033), herein incorporated by reference. Clarke '033 teaches that restenosis following angioplasty can be inhibited by application of UV radiation to the angioplasty site to kill smooth muscle cells which would otherwise proliferate in response to angioplasty-induced injuries to blood vessel walls.
Moreover, fiber optic delivery systems have been incorporated in endoscopic or catheter-based instruments to deliver photoactivating radiation to light sensitive drugs within a body lumen or cavity. U.S. Pat. No. 4,336,809 (Clark '809), herein incorporated by reference, and U.S. Reissue Pat. No. RE 34,544 (Spears '544), herein incorporated by reference, disclose that hematoporphyrin dyes and the like selectively accumulate in atheromatous plaque or tumorous tissue. These patents further teach that when cancerous tissue has taken up the dye, such tissue can be preferentially destroyed by radiation, typically by high intensity red light.
When a patient is catheterized with a light-emitting catheter that is inserted into the diseased artery or other body lumen, the placement is often likely to be offset from the longitudinal axis of the lumen. Such a configuration will result in a nonuniform exposure of the walls of the lumen by the light-emitting portion of the catheter. Nonuniform radiation exposure of the walls can result in damage to the lumen and/or nonuniform activation of the absorbed hematoporphyrin-like dyes.
In one embodiment of the Spears '544 patent, a light-emitting balloon catheter is employed to address the "centering problem." The catheter includes an inflatable balloon secured to the distal end of the catheter tube for inflation with gas from a remote source, and optical fibers which are disposed within the catheter, such that upon inflation of the balloon, light can be transmitted through the interior of the balloon to irradiate the target region of the lumen.
Although such a balloon catheter can act to center the light-emitting portion of the catheter, the balloon also acts to obstruct the flow of blood, therapeutic fluids, or air. Phototherapeutic treatments can take more than fifteen minutes. Thus, the duration of these procedures can preclude using a balloon catheter as a device for centering the light-emitting portion of the optical fiber since blocking a bloodstream or airway for an extended period of time is often impractical.
Accordingly, there exists a need for better apparatus for fiber-optic phototherapy. In particular, devices that can provide substantially uniform radiation exposure of a patient's lumen by centering a light-emitting catheter without occluding the lumen would meet a particularly important need in the field of minimally-invasive phototherapeutic surgery. Moreover, a device that can help stabilize the phototherapeutic instrument in operation (such as within an airway or blood vessel) would also be particularly useful. Uniform radiation exposure of the walls of the lumen while allowing flow of fluids past the light delivery device will make fiber optic phototherapy more practical and predictable.